1. Field of the Invention
The present invention relates in general to automatic transmissions and more particularly to control valve arrangements of the automatic transmission.
2. Description of the Prior Art
Japanese Patent First Provisional Publication 60-84451 shows a control valve arrangement of an automatic transmission. The control valve arrangement disclosed in the publication has a valve structure, which comprises upper and lower bodies coupled together with a separate plate intimately disposed therebetween. Each body is formed with a number of fluid passages, bores with free sliding spool valves, springs, and check balls. The lower body is received in a recess formed on an inner wall of a transmission case. The upper body is larger in size than the lower body and projects upward from the recess. A portion of the upper body extends sideward or laterally beyond an edge of the lower body to constitute a connecting portion. The connecting portion is formed with inlet and outlet openings of the fluid passages formed therein and is secured to a given portion of the transmission case through bolts. The given portion is formed with outlet and inlet openings of fluid passages formed in the transmission case. Thus, upon assembly, the inlet and outlet openings of the connecting portion of the upper body are mated with the outlet and inlet openings of the given portion of the transmission case thereby connecting the fluid passages of both parts.
However, due to its inherent construction, the above-mentioned control valve arrangement has the following drawback.
That is, since the connecting portion of the upper body, which is to be bolted to the transmission case, has therein the fluid passages leading to the inlet and outlet openings, the connecting portion tends to have a bulky construction. That is, in order to define mutually isolated fluid passages of sufficient size in the connecting portion, the size (viz., thickness or width) of the portion must be increased. In other words, in order to fulfill the requirement for additional fluid passages, the connecting portion by itself must deal with such requirement. Accordingly, the connecting portion must carry all the additional fluid passages because of its projected and isolated construction with respect to the lower body. As is known, increasing the size of such connecting portion means increase in size of not only the oil pan of the transmission but also the entire construction of the transmission, and thus causes a difficulty in mounting the transmission on a vehicle body.